Originally Posted by
TheChitterneFlyer
Though, I'm dumbfounded to understand why the absolute maximum couldn't allways be 100%... wouldn't that make more sense?
Not really.
Even assuming you were to choose the reference n1 value such that the maximum N1 allowed was 100% of the reference, you'd still have conditions where that was above the allowable maximum. Engines may be limited by temperature considerations, for example, and when these are more limiting the maximum N1 must be reduced.
Of course, you could have a more complex engine control scheme, so that instead of % N1 you were actually seeing "thrust %". But that would be far more complex to implement, and recall that this is a control numbering philosophy which predates FADECs. Also, any complexity is one more chance for something to be wrong - maintaining as simple a control scheme for the engines as practical makes sense in terms of minimizing exposure to errors in design implementation.
And finally, even if we did use "thrust %" instead of N1 (or EPR, for that matter) - which thrust shall we use? MTO? With APR/ATTCS boost? MCT? There's no simple, clean, answer.